Method of



1. 0. SAUNDERS. APPLYING FUSIBLE PLUGS T0 STEAM BOILERS No. 29,322. Patented July 24, .1860,

UNITED STATES PAEN T OFFICE.

ISAAC C. SAUNDERS, OF TLENTON, MICHIGAN.

METHOD OF APPLYING FUSIBLE METALLIC PLUGS TO STEA1VI-BOILERS.

Specification of Letters Patent No. 29,322, dated July 24, 1860.

To all whom it may concern:

Be it known that I, Isaac C. SAUNDERS, of Trenton, in the county of lVayne and State of Michigan, have invented a new and Improved Mode of Applying Fusible Plugs in LowJVater Alarms for Steam-Boilers; and I do hereby declare that the following is a full, clear, and exact description of the same, reference being had to the accompanying drawings, forming a part of this specification, in which Figure 1, represents a vertical longitudinal section; Fig. 2, a vertical cross sect-ion, and Fig. 3, a horizontal section of a boiler provided with my improved safety device.

Similar letters of reference, in each of the several figures, indicate corresponding parts.

To enable others, skilled in the art, to make and use my invention, I will proceed to describe its construction and operation.

(1, represents the fire box and b, the water jacket.

70, is a plug seat extending upward from an elevated semi-spherical base plate Z, which is placed over a hole y, in the top plate 2', of the fire box and is fastened to this top plate 2', by means of a circular flange 00, and suitable bolt-s. The plug seat is made with a conical hole 7', through its center, the base of the cone being on top as seen in Fig. 1. A fusible plug of corresponding conical shape is inserted into this hole j, in the plug seat.

A female screw 0, with another screw thread on its outer surface is screwed into the top of the boiler with a clamp nut 7), inside of the boiler so as to secure this female screw 0, in its place.

A cap 7 is screwed onto the top of 0, and the hollow space inside of the cap is filled with suitable material so as to form a stuffing box. A tube a, is inserted through this stuffing box and a male screw cut into the outer surface of tube 11-, screws into the female screw 0. The upper end of the tube n, is provided with a suitable head a, to which a screw wrench may be applied whenever it is desired to screw the tube a, up or down.

The top of the tube a, is closed by a little screw 8, screwed into its upper end. The lower end of tube a, is provided with a cap at, which when screwed down will fit over and close the plug seat, the centers of the plug seat and of the tube a, being in one line. The inside diameter of the tube a, is equal to or rather a little larger than the upper diameter of the conical hole A tube t, communicating with a hole 7', extends from the plug seat upward and through the top of the boiler. A steam whistle or other alarm apparatus maybe attached to its upper end.

When the water in the boiler becomes so low as to be in line with the upper extremity of the semi-spherical base Z, the plug seat is no longer surrounded with water and the heat in the fire box acting against the lower end of the plug seat will forthwith melt the fusible plug. Thus by making the base of the plug seat more or less elevated, the plug can be caused to melt at a given height of the water above the top of the fire box, and before the latter has been laid entirely bare so as to cause imminent danger of bursting the boiler.

hen the plug has been melted the steam rushes through the hole j, but as the plug seat j, is wider on top than at its lower end, part of the steam escapes through pipe z, and thus serves to give the alarm.

After the alarm has been given, it is no longer necessary to blow off the steam, and

to prevent this, I screw the tube n, and cap m, down upon the plug seat so as to shut up the communication bet-ween the steam and the hole j, and fire box. A new supply of water can then be let in and after removing the screw 8, a new slug can be dropped throughtube n, into the plug seat. The tube a, is then again closed by screw 3, and is screwed up so to raise the cap m, to its original position above the plug seat. A seal can be placed between the cap and the head v, so that any carelessness on the part of the engineer may be detected with the seal thus applied. If the engineer should allow the water to get too low, he will be compelled to break it before he can introduce a fresh supply and a new plug and thus his carelessness will be made known to the head man ager. By this means it will be seen all the steam can be retained in the boiler after the alarm has been given, while with the usual plug seats which have no adjustable means of closing them after the plug has been melted, all the steam must be allowed to escape into the fire box before a new plug can be inserted.

The plugs of the plug seats heretofore in use must be inserted from the inside of the fire box, which is very inconvenient while my improved plug seat can, at any time be supplied with a new plug from the outside of the boiler, and without stopping the generation of steam as above described. 1

The device a, Fig. 1, is intended to represent a modification of my plan of closing plug seats after the plug has been melted adapted'to one of the usualplug seats h. It consists of a screw rod f, screwing through a female screw. 0, inserted in thetop ot the boiler.

The upper end of the hollow part of the plug seat is made tapering and the lower end of the screw rod f, is somewhat pointed so as to fit into the tapering mouth of the plug seat when screwed down. By this means, the plug seat may be closed after the plug has been melted. This is an important feature in locomotive boilers, where it may become desirable when near the top of a grade to reach the top with the steam still in the boiler after the plug has been melted instead of allowing all the steam to blow oil into the fire box.

What I claim as my invention and desire to secure by Letters Patent, is-

1. The conical plug seat when formed on an elevated, semi spherical base, Z in combination with the hollow screw rod n in the manner and for the purpose herein described. 2. The combination of the cap m with the hollow screw rod, nplug seat jand semi-spherical base, Z in the manner and for the purpose described. 3. The peculiar manner herein described, of arranging, and combining, the tube, t with the plug seat, j. of semi-spherical base, Z and screw rod, nm for the purpose set forth.

4. The use of the head, 0 and the cap 1" for holding, a seal, to detect any carelessness, on the part of the engineer, as set forth.

' ISAAC O. SAUNDERS. Witnesses:

Goonwm Y. AT LEE, G. F. G. DIETERIOH. 

